API call unsuccessful: Error creating distribution

I am working with the Qualtrics API to create a Distribution to send a survey invite to a singular contact in a mailing list. I have successfully created a distribution via the Qualtrics UI, with all of the corresponding parameters so I know they should work. This is the key documentation I am working from: https://api.qualtrics.com/api-reference/reference/distributions.json/paths/~1distributions/post . Any insight would be greatly appreciated.
Thank you and here is the relavent info:
I receive this error when running as a script in python and posting in Postman:
 {"meta":
{"httpStatus":"400 - Bad Request",
"error":
{
"errorMessage":"API Call Unsuccessful: Error creating distribution",
"errorCode":"DEC_8"
},
"requestId":"cb1c2477-0755-49c5-8243-cdf5ed86308e"
}
}
 Here is url: https://.qualtrics.com/API/v3/distributions
header = {API-token: , content-type:"application/json"}
And the json payload:
{
    "message": {
        "libraryId": "UR_2488CVRwq2XH4B7",
        "messageId": "MS_a3G4NLBKv5wso1E"
    },
    "recipients": {
        "contactId": "CGC_sdvm6nTY2O0nKws",
        "mailingListId": "CG_VOOB22zHx9o2wVj"
    },
    "header": {
        "fromName": "Qualtrics Test ",
        "replyToEmail": "noreply@mydomain.com",
        "fromEmail": "noreply@mydomain.com",
        "subject": "Test Survey Distribution"
    },
    "surveyLink": {
        "surveyId": "SV_87isJC9tHvmSgex",
        "expirationDate": "2021-07-13T12:46:11Z",
        "type": "Individual"
    },
    "sendDate": "2021-07-06T12:46:11Z"
}